Conventional pneumatic tools, such as a pneumatic wrench, sander or grinder typically include a fluid driven motor comprised of a rotor having sliding vanes and mounted for rotation on ball bearings enclosed within a pressure-tight tool housing. The ball bearings are supported by front and rear end plates positioned on each end of a motor cylinder having an offset annular bore, relative to its external diameter and running parallel to the cylinder length. The rotor runs longitudinally through offset annular bore of the cylinder, in non-concentric alignment with an internal wall and concentric alignment with the external wall thereof, to provide a chamber internal to the cylinder bore along the length of one side of the rotor for receiving pressurized fluid, such as compressed air, entering from an inlet port leading into the chamber. The pneumatic tool housing is a pressure-tight casing alternatively referred to as a motor housing.
Lengthwise slots in a number of equidistant locations about the circumference of the rotor for receiving the vanes are known as rotary vane slots. The rotary vane slots each support a phenolic (or plastic) vane that radially slides within the slots as the rotor rotates, thereby enabling consistent contact of the outer edges of the vanes with the internal wall of the chamber. In combination with lubricating oil, when the rotor is rotating due to a flow of pressurized fluid, the sliding vanes act as rotating “seals” forming a boundary in the pressurized chamber at the union of the vanes planar surface areas with rotor slot walls and vane outer edges with cylinder wall as vanes enter and exit the pressurized chambered area. Sometimes vanes are biased radially outward in the rotor slots to maintain contact with the cylinder wall by spring tension. Springs are provided between the base of the slot and air-vane to maintain a sealed chamber upon startup, thereby so eliminating cogging or stalling prior to inertial momentum. Each time a vane enters the chamber, it receives pneumatic force upon a high-pressure side of its extended planar surface, due to a flow of pressurized fluid that is entering behind it from an adjacent inlet port usually situated on the circumferential edge of the motor cylinder at the start of the chambered area. The inlet port communicates with an inlet passage and valve body in the tool housing. The high-pressure fluid passes through the cylinder walls, surmounting mechanical resistance at the air vanes in the chambered area, to reach a low-pressure state at exhaust ports in the cylinder wall. The exhaust ports are generally located beyond a specified degree of arc from the inlet of the pressurized chamber, thereby causing the rotor to forcibly rotate in a direction from the pressurized inlet towards exhaust ports within the motor cylinder and tool housing. A pinion on the rotor's shaft transmits rotational force to a planetary gear set to provide useful torque conversion from high-speed rotation at the working end of the tool. Some pneumatic tools make use of gearing in order to transmit the rotational force to the working end of the tool, while others do so simply by employing a threaded shaft and a collet, or other means appropriate to the primary application of the tool.
U.S. Pat. No. 4,678,922 (Leininger), the contents of which are incorporated by reference in its entirety herein, discloses an apparatus for generating electricity using the flow of pressurized fluid such as air in a pneumatic tool by way of a magnetic coupling between a specially designed rotor and a stator. Magnetic means are affixed to the tool rotor, and thereby cooperate during rotation with a stator mounted in the tool housing, motor cylinder or bearing end plate(s) to induce electrical current in the coils of the stator. The '922 disclosure thus provides an integrated, self-contained and self-powered lighting source for illuminating a workpiece upon which the pneumatic tool is working. Various improvements have been made to integrated electricity generators in order to improve their electrical output, longevity, usability, efficiency, cost and manufacturability, and to reduce their size. Examples of such improvements may be found in U.S. Pat. Nos. 5,525,842 and 7,095,142 (both to Leininger), each incorporated by reference in its entirety herein, in which various configurations of rotor, stator, power distribution and light source are provided.
While the contributions of the above-mentioned references are significant, improvements are of course desired. For example, both the rotor and stator of prior art integrated electricity generators are inside the tool housing such that they are exposed to the compressed air and fluids containing lubricating oil mixed with moisture in the pressurized air stream flowing therethrough. The stator and particularly the coil winding therefore have to be potted or otherwise specially treated in order to protect sensitive electrical components. Furthermore, each device to which the generated electricity is supplied (i.e., incandescent lamps, light emitting diode (LED), active RFID tags and other electronic devices etc.) is typically employed by, or presents a user interface external to, the tool housing. Electrical lead wires conducting current from a stator must therefore pass from the pressurized interior of the tool housing, typically at 90 to 100+ pounds-per-inch2 (psi) during operation, to exterior zones typically at normal atmospheric pressure of zero psi, via feed-through conduits. To prevent leaks of pressurized fluid, an additional manufacturing step is typically necessary to provide hermetic sealing around the feed-through conduits. Additionally, during tool assembly and service a labor-intensive procedure is needed to resolve the physical placement of lead wires through a motor bore, tool housing and feed-through conduit from an internal stator.
Furthermore, it is an electronic challenge to provide a secure, vibration damped environment for mounting printed circuit boards containing sensitive integrated circuit (IC) components and sensors, whether on a metallic bodied tool surface or in a cavity thereon, while also providing a nonconductive and static-free and dry environment. Experience in the art teaches that pneumatic motor resonations can produce deleterious effects on some electronic components hard-mounted onto the tool housing.
It is an object of an aspect of the following to provide a novel integrated electricity generator for a pneumatic tool having a stator that is positioned external to the pneumatic tool housing.